U.S. Pat. No. 2,242,743 discloses a toothbrush having a handle 12, a head 14, and a plurality of tufts 16 of bristles which extend outward from the head. The tufts are positioned at an acute or obtuse angle with respect to the handle and head. The bristles provide a series of transverse, broad, inverted V-shaped areas on the working surface 18. The free ends of the bristles of each tuft form a surface which is inclined away from the direction in which the tuft is inclined.
U.S. Pat. No. 3,085,273 discloses a toothbrush having a handle 10 with an elongated head portion 12 formed integrally with the head. Bristles 14 are mounted in the head portion and are formed in tufts 15. The tufts are arranged in parallel rows 16, 16' longitudinally of the head and inclined in the direction of the rows. The free end of the bristles of each tuft define a plane which is perpendicular to the direction in which the tuft extends from the head.